Add ability to block "You won't be able to pull or push project code via SSH" message when SSH certificates are in use (or in general)
As noted in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19911#note_91196376 now that my !19911 (merged) is merged there's a UI problem when SSH certificates are used, in that mode users are expected to use SSH without uploading any key to their profile, but GitLab will show the "You won't be able to pull or push project code via SSH" warning regardless.
As @nick.thomas notes in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/19911#note_91874632 there should be an application setting to globally disable this notification, and suggesting enabling it it should be part of the SSH certificates documentation.
Edited by Ævar Arnfjörð Bjarmason